Theorem ([1]}, Proposition VII.4.6) 
Let \({A}\)  be a Banach algebra with identity, and let \(a \in {A}\) , and let \(G\)  be an open subset of \( such that \) (a) G\(. If \) = { 1, ..., m }\( and \) = { 1, ..., k }\( are two positively orientated collection of curves in \) G\( such that \) (a) insG\( and \) (a) insG\( and if \) f : G  is analytic, then
\(\int _\Gamma f(z)(z - a)^{-1} \,\mathrm {d}z = \int _\Lambda f(z)(z - a)^{-1} \,\mathrm {d}z\) 

